Success of Helicobacter pylori Guideline-based Treatment of Newly Diagnosed and Previously Treated Patients During 2007–2021 in Edmonton, Alberta

Abstract Background Updated 2016 Helicobacter pylori consensus guidelines recommend treatment for 14 days with concomitant therapy (proton-pump inhibitor (PPI)-amoxicillin-metronidazole-clarithromycin (PAMC) or bismuth-based quadruple therapy (PPI-bismuth-metronidazole-tetracycline, PBMT)) as first line, PBMT or PPI-amoxicillin-levofloxacin (PAL) as second or third line, and PPI-amoxicillin-rifabutin (PAR) as fourth line for 10 days. Objectives This was a retrospective cohort study to describe and compare the efficacy of anti-Helicobacter treatment regimens over the periods 2007–2015 and 2016–2021 as well as antibiotic resistance. Methods A modified intention-to-treat (mITT) analysis was used to analyze the success rate of therapies. mITT includes all patients who were prescribed H. pylori treatment and had at least one follow-up test-of-cure. This included patients who could not complete treatment or were non-adherent with treatment. Risk factors for treatment failures were analyzed by univariate and multivariate logistic regression. Resistance testing was done in a small subset of patients. Results H. pylori-positive patients who received treatment in Edmonton, Alberta were included in a mITT analysis: 334/387(86%) from 2007 to 2015 and 193/199 (97%) from 2016 to 2021. During 2016–2021, 78% (150/193) of patients underwent cumulative guideline-based treatment with a successful cure in 80% (120/150) of patients. In those who were newly diagnosed, the cure rate was 88% (52/59) versus those with previous treatment failure 75% (68/91) (P < 0.05, risk difference [RD] 14%, 95% confidence interval [CI] 1.7–26.3%). The most effective first-line regimens were PAMC for 14 days (87% [45/52]) in 2016–2021 and sequential therapy in 2007–2015 (83% [66/80]) (P = 0.535, RD 4%, 95% CI −8.5–16.5%). When other treatments failed, success with PAR was 50% (2/4) from 2007 to 2015 and 57% (21/37) from 2016 to 2021. Recent (2016–2021) resistance rates to clarithromycin and metronidazole are high at 78% (50/64) and 56% (29/52), respectively. From 2007 to 2015, clarithromycin and metronidazole resistance rates were 80% (36/45) and 83% (38/46), respectively. Levofloxacin resistance increased significantly from 2007–2015 to 2016–2021 (28% [13/46] to 61% [35/57], P < 0.05, RD 33%, 95% CI 11.6–54.4%). Conclusions Algorithmic treatment with PAMC first line followed by PBMT, PAL, and PAR cures H. pylori in 88% of newly diagnosed patients. PAR therapy shows suboptimal cure rates (50–57% success) but can be considered as third instead of fourth line given increasing levofloxacin resistance rates. Antibiotic resistance in H. pylori is common to clarithromycin, metronidazole, and levofloxacin and frequently accounts for treatment failures.


Introduction
Helicobacter pylori is an accepted cause of gastritis, dyspepsia, duodenal, and gastric ulcers and is a risk factor for gastric cancer.There is consensus that H. pylori-positive patients should be offered treatment.
Traditionally, therapy involved "classic" triple combinations of a proton pump inhibitor (P) with clarithromycin (C) and either amoxicillin (A) (PAC) or metronidazole (M) (PMC) for 7-14 days.These two combinations previously had efficacy rates >80-90%. 1,2However, these combination therapies are no longer recommended because of low success rates mainly attributed to resistance of H. pylori to antibiotics, particularly clarithromycin and also metronidazole. 3 Consequently, new treatment combinations have evolved.The 2016 Toronto H. pylori consensus and other international guidelines all make similar updated recommendations, [4][5][6][7] including treatment duration for 14 days.First-line therapies are concomitant therapy with a proton-pump inhibitor (PPI) and amoxicillin-metronidazoleclarithromycin (PAMC) or bismuth-based quadruple therapy (PPI-bismuth-metronidazole-tetracycline, PBMT).Recommended second and/or third-line therapies are PBMT or PPI-amoxicillin-levofloxacin (PAL) and the fourth-line PPIamoxicillin-rifabutin (PAR) given for 10 days.
Few studies have reported on the efficacy of H. pylori regimens in Canada, levels of antibiotic resistance, and changes over time.
The objectives of the study were to (1) compare the efficacy of different anti-Helicobacter regimens over the periods 2007-2015 and 2016-2021, (2) report the success rates of regimens when given as first-, second-, or higher-order treatments, (3) determine the cumulative success rate when patients were treated in sequence with different regimens, (4) provide data on antibiotic resistance, and (5) determine predictors of treatment success.

Methods
This retrospective study reviewed records of patients treated for H. pylori infection at the University of Alberta Hospital (UAH), a tertiary referral centre in Edmonton, Alberta from January 1, 2007 to June 1, 2021.Given recent updates to clinical practice guidelines, therapeutic regimens from a previous era of treatment (2007-2015) are compared to the current era of treatment (2016-2021).Separately, data on antibiotic resistance in H. pylori are reported from 1999 to 2021.The Strengthening the Reporting of Observation Studies in Epidemiology (STROBE) guidelines were used in the reporting of data. 8tients Patients seen at UAH were either newly diagnosed or previously treated for H. pylori infection.Participants were eligible for study inclusion if they were ≥18 years of age and had a diagnosis of H. pylori infection confirmed by at least one of a 13 C urea breath test (UBT), histology, culture, or Helicobacter stool antigen test (HpSAT).Exclusion criteria included age < 18 years or if there was no documented test of the presence of H. pylori infection prior to treatment.One physician (SVvZ) treated the vast majority (90%) of patients, so no comparisons were made among physicians regarding treatment choices.
Data were collected on patient demographics, method of H. pylori diagnosis, treatment regimen(s) prescribed, duration of therapy, post-treatment eradication testing, number of courses of antibiotics prescribed for H. pylori, and success of therapy.For all patients, it was determined whether they had received anti-Helicobacter treatment before they were referred to UAH and what regimens were used, although it was not always possible to get precise information on previous treatment regimens.Compliance and side effects were not formally assessed.They were only recorded if patients reported problems in taking all the prescribed medications or if treatment was stopped because of side effects.

Diagnostic tests used
Diagnosis of H. pylori infection and test-of-cure (TOC) were documented with a 13 C UBT, HpSAT, or positive histology on endoscopic biopsies.For some patients, more than one test was available.For histology routine, hematoxylin and eosin staining was used, and sometimes, a modified Giemsa or Warthin-Starry (silver stain) was used at the discretion of the pathologist.A well-validated 13 C UBT was used (Helikit R UBT, Isodiagnostika, Edmonton, Canada).In all patients, TOC was performed at least > 4 weeks after the anti-Helicobacter therapy was completed.In the majority of patients, repeat testing was done 4-8 weeks after anti-Helicobacter therapy was completed.
Cultures of H. pylori were available in some patients but never used alone to establish diagnosis.Details on cultures of Helicobacter pylori and resistance testing are listed in the Supplementary File.

Data analysis
For treatment results, a modified intention-to-treat (mITT) analysis was used that included all patients in whom treatment was prescribed with at least one subsequent TOC (Figure 1).This included patients who could not complete treatment or were non-adherent with treatment.The Chi-square test was used to determine P-values for categorical variables and the T-test used for numerical variables.For all treatment results, 95% confidence intervals (CI) were calculated. 9For risk factor analysis of treatment results, univariate and multivariate logistic regression was performed in SPSS (IBM®).

Reporting of results
Cumulative results are reported separately for those patients who received their first guideline-based anti-Helicobacter treatment at UAH (newly diagnosed, treatment naive) and treated according to the guidelines, i.e., sequential therapy during 2007-2015 and concomitant therapy (PAMC) during 2016-2021 as first line.If these therapies failed, further treatments were also guideline-based.Separately, results are also reported for those patients who had received one or more treatments prior to being seen at UAH.Their subsequent choices of therapy were also guideline-based.For example, if a patient had failed a clarithromycin-based regimen, use of clarithromycin was avoided in subsequent treatments.In those patients in whom cultures and resistance data were available, the treatment choice was also guideline-based.If a patient's H. pylori strain was resistant to clarithromycin or levofloxacin, those regimens were avoided.If a patient was resistant to metronidazole but sensitive to levofloxacin, PAL was given before PBMT.Resistance to amoxicillin was not used in treatment decisions.
The study was approved by the Research Ethics Review Board at the University of Alberta.As this was a retrospective study with a de-identified analysis of patient data, the need for individual patient consent was waived.

Results
Table 1 lists the various regimens that were used including dosages.It should be noted that in 2016, duration was changed for most treatments from 10 to 14 days except for Rifabutin-based therapy (PAR).The difference between Sequential and Concomitant (PAMC) therapy was not only the duration of therapy (10 vs. 14 days) but also the duration of antibiotics given.For sequential therapy, amoxicillin is given for 5 days (day 1-5) followed by 5 days clarithromycin and metronidazole (day 6-10).In concomitant therapy, all three antibiotics are given for the full 14 days.
Bismuth-based quadruple therapy, when given as secondline therapy, had an efficacy of 56% ( 59 The data demonstrate that if guideline-based therapies are followed in sequence, high success rates can be achieved after three or four rounds of therapy.The cure rate of the cumulative guideline-based approach of patients first treated at UAH was 86% (69/80) during 2007-2015 (Sequential-PBMT-PAL-PAR) and 88% (46/52) during 2016-2021 (PAMC-PBMT-PAL-PAR).
Logistic regression was used to identify predictors of treatment success (Table 3).Univariate analysis identified being treated first at UAH as a predictor of treatment success (odds ratio [OR] = 3.177, P = 0.003, 95% CI 1.476-6.840).Previous exposure to clarithromycin (OR = 0.461, P = 0.03, 95% CI 0.299-0.927),metronidazole (OR = 0.232, P < 0.001, 95% CI 0.117-0.458),and amoxicillin (OR = 0.441, P = 0.19, 95% CI 0.222-0.876)were negatively associated with successful treatment.The forward selection (likelihood ratio) method was used to select being born outside Canada, and previous Metronidazole exposure as variables for multivariate analysis, with treated first at UAH added to the model due to the strength of effect on univariate analysis.Previous metronidazole exposure was negatively associated with treatment success (OR = 0.290, P = 0.007, 95% CI 0.118-0.713);however, other antibiotic exposures did not add to the model.Being treated first at UAH was not an independent predictor of cure on multivariate analysis (OR 1.687, P = 0.326, 95% CI 0.595-4.785).Overall, 75% (8/12) of penicillin-allergic patients were cured, with 5/6 (83%) of them cured with first-line PBMT.
The results of bacterial cultures and antibiotic resistance levels are reported in Table 4. Data from Nova Scotia from 1999 to 2006 is described that was previously only reported   No cases of resistance to tetracycline were observed between 2007 and 2021.Resistance to amoxicillin was not seen in any of the 157 strains analyzed in Halifax during 1999-2006 11 or in the 41 Edmonton strains obtained during 2007-2015.There were four cases of amoxicillin resistance during 2016-2021: 10% (1/10) primary resistance and 8% (3/36) secondary resistance.All cases of amoxicillin resistance were slightly above the European Committee on Antimicrobial Susceptibility Testing (EUCAST) MIC of 0.0125 mg/L. 12It is unclear whether this signifies true amoxicillin resistance.

DISCUSSION
][6] Important recommendations were made, including: 1. that most treatments should have a duration of 14 days, 2. that a clarithromycin containing regimen should not be used, if a prior clarithromycin-containing regimen had failed, 3. recommended first-line therapies are either concomitant (PAMC) therapy or bismuth-based quadruple therapy (PBMT) 4. bismuth-based quadruple therapy or alternatively the combination of PPI, amoxicillin, and levofloxacin are good second and third-line options, 5. fourth line therapy is the combination of PPI, amoxicillin, and rifabutin.6. Use of the triple-combination of a PPI with clarithromycin and either amoxicillin or metronidazole is no longer recommended.
Generally, Concomitant (PAMC) therapy is preferred over Bismuth-based quadruple therapy as first-line treatment, as PBMT is more cumbersome to take and has more side effects.
PBMT is recommended as first line in patients with penicillin allergy.Concomitant (PAMC) performed well as a first-line therapy with a success rate of 87% compared to a 83% first-line cure rate with sequential therapy during 2007-2015, although this difference was not statistically significant.A meta-analysis comparing concomitant to sequential therapy in 14 studies showed concomitant therapy was significantly more effective than sequential therapy ITT eradication rate, 85.7% versus 79.7% with a statistically significant RD of 6%). 4 The data confirm (figure 2) that once a patient fails a first line therapy that success rates with subsequent therapies are not as high.The most common reason is resistance of H. pylori to antibiotics. 3,4Logistic regression of predictors of success (Table 3) did show that previous exposure to clarithromycin, metronidazole, or amoxicillin was negatively associated with treatment success.Furthermore, concomitant therapy, used as first-line therapy, is also a predictor of success, reiterating that it is important that treatment guidelines are followed.
Other 2016 data from Canada reported a cure rate of 81% per protocol (PP) and 75% ITT in 175 patients, who failed first-line treatments. 13Using seven different treatment combinations bismuth quadruple therapy given for 7,10, or 14 days for the first failure or for 14 days for second to fifth failure was superior to all PPI triple therapies: BMT 91%, PP < 84% ITT, triple therapy PP 66%, ITT 62%. 13ata from the European Registry on H. pylori Management (Hp-EuReg) consortium supports the use of the management algorithm PAMC-PBMT-PAL-PAR. 14The main explanation for the decrease in efficacy of PAC and PMC is the markedly increased resistance of H. pylori against clarithromycin, also observed in Canada. 2,7,8Fallone et al., in a 2000 review, reported resistance rates of 4% to clarithromycin and 18-22% to metronidazole. 15Resistance data obtained from arctic communities living in the Yukon and the Northwest Territories show similar rates. 16Our culture data, although based on a small sample size, show that background resistance to clarithromycin is currently much higher, justifying why the PAC or PMC combinations should be avoided.However, these data should be interpreted with caution as they mainly reflect patients who were treated with this therapy and failed and subsequently were referred to the UAH.
As can be seen in Table 4, during 1999-2006, primary resistance to clarithromycin was substantial at 15% (37/ 245) and secondary resistance at 56% (137/245).Data for the period 2007-2021 show very high levels of resistance to clarithromycin, ranging from 59% to 85%.Data on resistance to levofloxacin also show high rates of resistance of 19% (30/157) during 1999-2006 and ranging from 20% to 59% during 2007-2021.This is likely due to the frequent use of quinolones for other indications.The high background resistance rate to levofloxacin is the reason why the use of levofloxacin is not recommended as part of first-line therapy. 3orldwide resistance to amoxicillin is low, and we found the same in our patients.However, in the four strains with amoxicillin resistance, the MICs were all slightly above the EUCAST breakpoint of 0.125 mg/L.It is unclear whether this signifies clinically significant amoxicillin resistance.Resistance to tetracycline was not observed in any of the isolated strains during the 2007-2021 period.Thus, both amoxicillin and tetracycline are excellent antibiotic choices for H. pylori therapy.
Over the last 25 years, rates of metronidazole resistance rates have consistently remained high but have risen from 25% primary resistance during the period 1999-2006 to 40-88% during the periods 2007-2015 and 2016-2021.8][19] We found that dual resistance to metronidazole was found in 46% (23/50) of clarithromycin-resistant strains.It is known that the presence of this type of dual resistance is a strong predictor of treatment failure when clarithromycinmetronidazole regimes are used. 3ata on antibiotic resistance in the USA are also scarce.Rising USA resistance rates in a recent meta-analysis were reported: clarithromycin 25%, metronidazole 45%, levofloxacin 22%, tetracycline < 2%, and amoxicillin <2%. 20In a recent study of 907 mainly American and European patients, resistance rates to clarithromycin were 22.2%, metronidazole 69.2%, and amoxicillin 1.2%, and among clarithromycinresistant isolates, 75% were also metronidazole-resistant. 21 Worldwide data also report rising rates of resistance of H. pylori strains. 22t is important for clinicians to keep these resistance data in mind when choosing H. pylori therapies.Ideally, local data on resistance profiles of H. pylori are known, but in reality, this is seldom the case.In the absence of local resistance data, the best substitute is regular assessment of success rates of treated patients to document whether they conform with expected levels of success.
Although side effects were not formally assessed in detail in our patients, treatment generally was well tolerated.The large majority of patients were able to finish the entire course of therapy.High compliance may be in part facilitated by the fact that all our patients receive a detailed handout explaining the importance of H. pylori infection and providing instructions on when the different treatments should be taken.Furthermore, all our prescriptions are written as blister packs to facilitate compliance.Hp-EuReg documented that compliance generally is high, >97% and serious side-effects are rare, 0.08%. 23In some countries, including the USA and parts of Europe, a triple combination tablet is available for the combination of bismuth, metronidazole, and tetracycline, and the efficacy of this medication has been reported as 90% as first line and as rescue therapy. 24,25antoprazole at 83% was by far the most commonly used PPI as part of H. pylori treatment.It is also the most common PPI prescribed in Alberta as it is preferentially listed by the Alberta provincial drug plan.However, using a comparison to 20 mg omeprazole equivalents, pantoprazole 40 mg is one of the weaker PPIs. 26Hp-EuReg data show that by using more potent PPIs (such as esomeprazole 40 mg bid or higher), there is a slightly higher cure rate. 27More potent acid suppression may also be the explanation why the potassium competitive inhibitor inhibitor vonoprazan (not available in Canada currently) has higher cure rates of H. pylori infection than lansoprazole when combined with clarithromycin and amoxicillin. 28n Canada, the combination of PPI, amoxicillin, and rifabutin has been mainly used as fourth-line rescue therapy.The success of this combination in 2010 used as fourth-line rescue therapy was 62%. 29Since 2019, a combination tablet of omeprazole, amoxicillin, and rifabutin (Talicia ® ) has become available in the USA, and the success rate of this 10-day regimen given as first line was 84%. 30In Canada, to date, rifabutin is a restricted drug, and special authorization for its use needs to be requested, and the combination table is not available.Another limitation is that rifabutin is expensive.The limited data on rifabutin resistance to date have shown very low levels of resistance. 20,30Rifabutin can cause myelotoxicity, but in treatment for H. pylori, this is rare, 7,31,32 and no cases were observed in our patients treated with rifabutin.
Given the high levels of resistance to levofloxacin we observed, consideration should be given to using PAR as third-line therapy.It is acknowledged that the success rate of PAR therapy of 50-57% observed is suboptimal, even when given as rescue therapy.More studies of rifabutin are required to see if changes to the duration of treatment, dosages of drugs used, or use in combination with other agents, such as bismuth compounds, could increase treatment efficacy.Given the high levels of metronidazole resistance, a change in bismuth quadruple therapy could also be considered by using amoxicillin instead of metronidazole.Finally, another management option after multiple treatment failures is the decision not to treat H. pylori any further but possibly observe these patients long term.Long-term follow-up especially is a consideration if there is a family history of gastric cancer or if gastric metaplasia was present on histology. 33imitations to the study include the fact that this was a retrospective single-centre study.Therefore, the results may not be generalizable.Patients were only included if a TOC was available after treatment.Data capture on levels of adherence, tolerability, and adverse events associated with regimens was limited.Some patients were treated in the community prior to referral, so their treatment information could have been incomplete, but all efforts were made to identify previous anti-Helicobacter treatment regimens.The number of Edmonton patients in whom culture and antibiotic sensitivity data was available was small, and this was especially true for treatment-naïve individuals.However, data from Canada on H. pylori cultures and resistance are very limited.For this reason, resistance data from 1996 to 2006 from Halifax, Nova Scotia were included as it is a large dataset, even though it was not derived from the patient cohort reported in this study.The Halifax data help to show the changes in antibiotic resistance of H. pylori strains over a longer period in Canada.
The Edmonton culture data from 2007 to 2021, although based on a small sample size, show important findings of the background resistance to antibiotics, that is, high levels of resistance to clarithromycin, metronidazole, and levofloxacin and low levels to amoxicillin and tetracycline.

Conclusions
This real-world study shows that following existing guidelines with algorithmic treatment with PAMC first line followed by PBMT, PAL, and PAR is effective at eradicating H. pylori infection in 88% of newly diagnosed patients.Antibiotic resistance in H. pylori is common to clarithromycin, metronidazole, and levofloxacin and frequently accounts for treatment failures.Ideally, culture and sensitivity testing should be done to understand resistance patterns in H. pylori but TOC data is an important substitute to document the success rates of treatments that are used in the community.Rifabutinbased regimens perform suboptimal (50-57% cure rate) and require more study for optimization, however, may be considered as third-line therapy due to increasing levels of levofloxacin resistance.
below for doses that differed from the recommended doses by the Toronto consensus guidelines 4 a Recommended dose of Bismuth subsalicylate is 250-500 mg PO QID.b Recommended dose of Levofloxacin is 250 mg PO BID.c Recommended dose of Rifabutin is 150 mg PO qd.

Figure 2 .
Figure 2. Comparative success rates of H. pylori treatment regimens during the 2007-2015 and 2016-2021 periods in newly diagnosed and previously treated patients (modified intent-to treat analysis, with all subjects included in analysis unless there was no follow-up/test-of-cure after their first treatment regimen).

Table 1 .
Description of the treatment regimens used for H. pylori infection.

Table 3 .
Predictors of treatment success in patients treated for H. pylori 2016-2021, logistic regression.

Table 4 .
H. pylori antibiotic resistance rates in Canada from 1999 to 2021.
10ta from 1999 to 2006 were collected from Halifax, Nova Scotia; data from 2007 to 2021 were collected from Edmonton, Alberta.For details, see text.Determination of resistance based on European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints for H. pylori antibiotic resistance.Reported cases of amoxicillin resistance were all slightly above the EUCAST MIC of 0.0125 mg/L.10.